In the search for cathode mixes which show maximum discharge performance, cathode mixes with different electrolytic manganese dioxide (EMD) and graphite compositions have been investigated in a flooded test cell assembly. Variation in performance with particle size, both EMD and graphite, was observed. In general, performance improved with higher amount of graphite and finer particle size. Both lower open circuit potential and significantly better performance towards the lower potential range of the discharge occur with carbon black present. The influence of combinations of graphite and carbon black with high surface area has also been examined. The information gained can be used to better explain the influence of selected cathode materials in batteries.